Carburetor



Feb. 15, 1944. 1. E. COFFEY 2,341,694

GARBURETOR Filed Oct. 12, 1940 INVENTOR IRVEN E. COFFEY @Mufg- ATTORNEYTip-- Patented Feb. 15, 1944 CABBURETOR Irven E. Coffey, Normandy, Mo.,assignor to Carfor Carburetor Corporation, St. Louis, Mo., a corporationof Delaware Application October 12, 1940, Serial No. 360,979

11 Claims.

- This invention relates to carburetors for internal combustion enginesand, more particularly, to compensating means for variations in flow ofvolatile liquid fuel due to temperature change.

Carburetors in general and particularly downdraft carburetors, due totheir location with respect to the engine, become heated to such extentdue to high speed driving on warm days that the usually available fuels,upon being received in the carburetor constant level chamber,immediately become charged with vapor bubbles. It will be readilyappreciated in view of this that the amount of fuel, by weight, in thiscondition which will pass the relatively small fuel metering orifices,which control the flow to the carburetor mixture conduit, will be lessthan if the fuel were cool and not boiling. This, obviously, results ina leaning out of the mixture, and frequently, in practice, causesobjectionable irregularity of engine operation known as surging.

It is the primary object of the present invention to provide an improvedcarburetor including automatic means for increasing the volume of fueldischarged into the mixture conduit when said fuel becomes charged withvapor due to heating.

It is a further object of the present invention to provide a carburetorof the above character in which restriction of the flow of fuel from theconstant level chamber to the mixture conduit is automatically decreasedas the fuel reaches a temperature whereby its flow, by weight, to saidmixture conduit is decreased by reason of its boiling.

It is a further object of the present invention to provide a carburetorof the above character having air bled fuel jets and including tempera-'ture-responsive means for reducing the air bleeding of the jet as thefuel reaches a temperature whereby its flowby weight through the jet isdecreased by reason of its boiling.

Further objects and advantages will become apparent upon reference tothe following description and accompanying drawing referring to which:

Fig. 1 is a diagrammatic view of a downdraft carburetor embodying a formof the present invention.

Fig. 2 is a fragmentary view of the carburetor shown in Fig. 1 showing amodification of the metering device.

Numeral 1 indicates a main carburetor body member having a mixtureconduit 2 formed therethrough. The lower end of body .I is equipped witha flange 3 for attaching the carburetor to the intake manifold of aninternal combustion engine. The mixture conduit is provided with aventuri formed restriction 4 and two concentric Venturi tubes 5 and 6suspended therein. The outlet of the mixture conduit is controlled by aplate-type throttle valve I mounted for rotation with a throttle shaft8. ,Adjacent the mixture conduit and formed as an integral part of bodymember I is a constant level fuel chamber 9 equipped with a float IIIwhich acts upon the intake needle valve H to maintain a substantialconstant level of fuel as indicated by the dot-dash line A-A.

Attached to the upper end of body member I is a combination air inletand fuel chamber cover casting [2 having an air inlet l3 to the mixtureconduit formed therein. For control of the air inlet an unbalancedplate-type choke valve ll rigidly attached to'a rotatable choke shaft I5is provided. Enclosed in a housing IE on the far side of casting I2 is abi-metallic temperature responsive spiral ll which has its inner endattached to shaft l4 and its outer end abutting a stop l8. The elementI1 is so constructed as to tend to unwind with decreasing temperaturethereby urging the valve 14 in a counter-clock wise direction toward aclosed position.

Discharging into the Venturi tube 6 is a main fuel nozzle l9 whichreceives fuel from chamber 9 through the metering orifice 20 and passage43. Extending through the orifice 20 is a stepped and tapered meteringrod 2| arranged to be moved vertically to vary the net opening of theorifice. Link mechanism is provided for positioning the metering rod inaccordance with the position of the throttle valve comprising a lever22, which is pivoted at 23, a link 24, and a lever 25 which is rigidlyattached to the throttle valve shaft 8. In order to compensate for thereduction in flow through orifice 20 at high bowl temperatures and ,atwhich the fuel becomes charged with vapor bubbles, the metering rod 2|is constructed in two sections which are joined by the bi-metaltemperature responsive loop 26. Element 26 is so constructed as to raisethe lower end of rod 2| with increasing temperatures and therebyincrease the net opening of orifice 20 for any given position of thethrottle valve.

Fuel is supplied to the mixture conduit for low speed operation throughan idling system comprising an idling fuel jet .21, a passage 28, an airbleed 29, a restricted passage 30, an air bleed 3|, a passage 32, 33 anddischarge ports 34 and 35. In order to compensate for the reduction inflow, through the small idling jet 21, due to boiling of fuel, athermo-control of the air bleed 3| is provided. This control comprises aball valve 36 adapted to be seated on a valve seat 31 at the upper endof passage 32 thereby closing bleed 31. The ball 36 is supported on abi-metal temperature responsive helix 38 which is so constructed as toextend with increasing temperatures thereby urging ball 36 toward theseat 31 and reducing the effectiveness of the air bleed therepast. Itwill be understood that the element 38 by reason of its structureprovides a yielding support for ball 36 and its tension, while varyingwith the temperatures, likely to be encountered, will, under any fueltemperature, permit the unseating of ball 36 when acted upon byabnormally high engine manifold vacuums which are communicated topassage 32 through ports 34 and 36. By "abnormally high manifold vacuum"is meant vacuum in excess of that necessary to hold the engine at anormal idling speed, such high vacuums are encountered when a motorvehicle is travelling at a high rate of speed down an incline with thethrottle substantially closed. The manner of forming and the operationof helical coil 38 is more fully explained in the patent to F. A.Parsons 2,121,259 for a thermostatic element similar to that employed inthe present invention. Thermostatic, elements of this construction arecommercially produced at present.

In the modification shown-in Fig. 2 a second fuel orifice 39 is providedfeeding the passage." and is controlled by a metering rod 40. The rod 40has a comparatively large diameter portion 40a which substantiallyrestricts the orifice 39 when in the position shown. It will be seenthat as the rod 40 is moved either upward or downward the restriction oforifice 39 will decrease. The rod 40 is attached at its upper end to aSylphon type temperature responsive element 4| which in turn is rigidlyattached to the carburetor at 42. The element M is so constructed as toexpand with increasing temperatures to, move rod 40 downward and is socalibrated as to assume the position shown in Fig. 2 during normaloperating temperatures. At abnormally low temperatures the element 4|will retract and move rod 46 upward thereby augmenting the flow throughorifice 20. Also at abnormally high temperatures the rod 40 will bemoved downward to a less restricting position thereby permitting anincreased flow by volume when the fuel is charged with vapor. In thisarrangement the metering rod 2| is formed in one piece, the temperatureresponsive element 26 being omitted.

In operation upon starting a cold engine, choke valve M will be in apartially or fully closed position by reason of heat responsive elementl1 and as a result an abnormally rich mixture for starting and warmingup of the engine will be delivered to the-mixture conduit by reason ofthis choking effect. As the engine attains a normal operatingtemperature, the element l1 will relax its tension by reason of heatabsorption from the engine and permit the oif-set valve II to assume awide open position after which it will have no enriching eilfect uponthe mixture as supplied to the normal operating calibration. If,however, the engine is operated at high speed or under load andtemperature conditions resulting in suflicient heating of the engine andthe attached carburetor to cause the. fuel in bowl 9 to boil, theelement 26 will respond to lift the lower portion of rod 20 to somedegree and the element 38 will respond to move ball 36 toward its seatthereby compensating for the normal leaning out due to the boiling ofthe fuel as heretofore explained.

The foregoing description and accompanying drawing are intended to beillustrative and not limiting and the use of all modifications withinthe scope of the appended claims is contemplated.

I claim:

1. In a carburetor having a mixture conduit and a constant level fuelchamber, a fuel passageway for conveying fuel from said chamber to saidconduit, a regulable metering orifice in said passageway calibrated topass the correct amount, by weight, of liquid fuel to said mixtureconduit for normal temperature operation, and a temperature thereforresponsive element submerged in and responsive to the temperature of thefuel acting to maintain predetermined restriction of said orifice duringnormal operating temperatures and to increase the net opening in saidorifice when the boiling temperature of the fuel is reached so as tocompensate to some degree for the reduction in fuel flow therethrough byweight due to the presence of bubbles in the fuel.

2. In a carburetor having a mixture conduit, a throttle valve in saidconduit, a constant level fuel chamber, a fuel passageway for conveyingfuel from said chamber to said conduit, a fuel metering valve forregulating said fuel passageway, link mechanism connecting said meteringvalve and said throttle valve, and a temperature responsive elementinterposed in said link mechanism and responsive to boiling temperatureof the fuel to increase the opening of said metering valve for a giventhrottle position to compensate for the formation of bubbles in thefuel.

3. In a carburetor, a fuel passageway, a metering orifice in saidpassageway, a metering rod extending through said orifice. said rodhaving an extended portion of its length of such diameter as touniformly restrict said orifice and having portions of lesser diameterat either end thereof whereby when said rod is moved in either directionfrom its greatest restricting position the net opening of said orificewill be increased, and means responsive to the fuel temperature formoving said rod to less restricting positions when the fuel temperatureis below normal and also when boiling temperature of the fuel isreached.

4. In a carburetor, a constant level fuel chamber, a mixture conduit, aliquid fuel passageway leading from said chamber to said conduit, 9.metering orifice in said passageway, a valve in said orifice, and athermostatic element normally submerged in said fuel chamber andconnected to said valve, said element being constructed and arranged tomove said valve toward a less restricting position as the fueltemperature exceeds the point where bubbles form therein.

5. In a carburetor having a mixture conduit and a constant level fuelchamber, a fuel passageway for conveying fuel from said chamber to saidconduit, valve means for said passageway, and a. temperature responsivedevice submerged in the fuel and connected to said valve, said de-,-vice being responsive to boiling temperature of the fuel to move saidvalve to a more open position so as to permit a greater flow by volumethrough said passageway when vapor bubbles are formed in the fuel.

6. In a carburetor, an induction conduit, a fuel bowl, a fuel passageconnecting said bowl and said conduit, an air bleed duct connecting withsaid passage, a valve seat and a valve therefor in said duct, and athermostatic spring responsive to boiling temperature of the fuel tourge said valve toward its seat with increasing force so as to reducesaid bleed and thereby compensate for the reduction in weight of fueldrawn through said passages due to boiling.

7. In a carburetor, a fuel passageway, a valve controlling saidpassageway, and a thermostat responsive to the fuel temperature andacting on said valve to restrict said passageway at normal operatingtemperatures and to reduce said restriction at lower fuel temperaturesto enrich the mixture and also at the boiling temperature of the fuel tocompensate for the formation of bubbles in the fuel.

'8. In a carburetor, an induction conduit, 9. fuel passageway disposedto discharge into said conduit according to the suction therein, and athermostatic valve device controlling said orifice and responsive tonormal operating fuel temperatures to restrict said orifice andresponsive to lower fuel temperatures and also to the boilingtemperature of the fuel to increase the net opening in said orifice.

9. The method of maintaining stable proportioning of fuel and air in thecombustible mixture supplied to an internal combustion engine whichconsists in metering the fuel supply in accordance with suction undernormal fuel temperature conditions and utilizing a fuel temperatureresponsive device for increasing the volume of the fuel supplied,responsive to heating of the fuel above the boiling point thereof tocompensate for the reduction in density of such fuel due to theformation of bubbles therein.

10. In a carburetor, an induction conduit, a fuel bowl, a fuel passageconnecting said bowl and said conduit, an air bleed for said passage, avalve controlling said bleed, and a thermostat controlling said valveand responsive to the boiling temperature of the fuel to decrease theeffectiveness of said bleed so as to compensate for the reduction inquantity of fuel supplied due to the formation'of bubbles therein.

11. In a carburetor, an induction conduit, a throttle valve therein, afuel bowl, main and idling fuel passages discharging-into said conduit,respectively, anterior and posterior to said throttle valve when closed,an air'bleed opening into said idling passage, a valve controlling saidbleed, and a thermostatic spring located in said idling passageandresponsive to the boiling temperature of the fuel therein to increasethe closing pressure applied to said valve and thereby decrease theeffectiveness of said bleed so as to compensate for the reduction inquantity of fuel supplied through said idling passage due to theformation of bubbles therein.

, IRVEN E. COFFEY.

